The CombiRx clinical trial is a randomized, double blind, placebo controlled, multi-center randomized study of the efficacy of combining interferon beta-la (IFN) and glatiramer acetate (GA) compared to either agent alone as primary therapy for relapsing-remitting MS (RR MS). The original funding of this NINDS sponsored project was in November 2003. Initially funding was requested for 40 clinical sites across North America. After funding, and based on consultation with NINDS program staff, the number of planned sites was increased to a target of 80 to improve recruitment. The recruitment goal is 1000 subjects, randomized 50% to combination therapy and 25% to each single therapeutic agent with a matched placebo. This application is for renewal of this grant to complete the follow up of all patients through three years on study protocol. The primary outcome and other outcome measures are unchanged from the original protocol and we have expanded the analyses to better assess disability progression. The continuation plan, which is to follow all subjects in their original study arm until the last subject has completed all three years of the study, has been approved by the study DSMB as well as the investigators.